The Russian submarine Novorossiysk surfaced off the coast of France last week and was later escorted by the Dutch navy in the North Sea, reportedly due to a fuel leak.

NATO chief Mark Rutte mocked the incident, calling the vessel a “lone and broken Russian submarine limping home from patrol” and joking it resembled a hunt for a mechanic rather than a military mission.

Russia’s Black Sea Fleet denied the surfacing was due to a malfunction, saying the submarine was following navigation rules in the English Channel and completing a “scheduled inter-fleet transit” after Mediterranean operations.

The sighting comes amid other reports of Russia’s “shadow fleet”—aging, obscurely owned vessels operating without Western-regulated insurance—which has raised environmental and safety concerns, Euro News has reported.

NATO and French authorities are monitoring such vessels closely, emphasizing maritime vigilance and readiness to defend the Alliance.